Method for reducing interference fringes by moving timing of triangular motion

Abstract

A method for reducing fringe interference of light created in a passive cavity defined by partially reflecting optical surfaces in a laser spectroscopy system, wherein the optical path length of the cavity is varied with a triangular back-and-forth movement (x). In accordance with the invention, the spectroscopic measurement is performed in successive measurement cycles with a time interval between each two successive measurement cycles, the triangular movement is performed such that the turning points of the triangular movement (x) are positioned in successive ones of the time intervals, and after each or at each n-th measurement cycle, the time position of the turning points is moved relative to the measurement cycle.

The invention claimed is: 
     
       1. A method for reducing fringe interference of light created in a passive cavity defined by partially reflecting optical surfaces in a laser spectroscopy system, wherein the optical path length of the cavity is varied with a triangular back-and-forth movement, the method comprising:
 performing a spectroscopic measurement in successive measurement cycles at a time interval between each two successive measurement cycles; 
 performing the triangular back-and-forth movement such that turning points of the triangular back-and-forth movement are positioned in successive ones of time intervals; and 
 moving a time position of the turning points relative to the measurement cycle after each or at each n-th measurement cycle. 
 
     
     
       2. The method of  claim 1 , wherein a length of the time interval is constant and a relative movement of a time position of the turning points is performed by one of lengthening and shortening back-and-forth movement sections of the triangular back-and-forth movement. 
     
     
       3. The method of  claim 1 , wherein a relative movement of a time position of the turning points is performed by one of lengthening or shortening the time interval. 
     
     
       4. The method of  claim 1 , wherein a relative movement of a time position of the turning points is performed randomly. 
     
     
       5. The method of  claim 1 , wherein a relative movement of a time position of the turning points is performed incrementally back-and-forth between a beginning and an end of the time interval. 
     
     
       6. The method of  claim 2 , wherein the relative movement of the time position of the turning points is performed incrementally back-and-forth between a beginning and an end of the time interval. 
     
     
       7. The method of  claim 3 , wherein the relative movement of the time position of the turning points is performed incrementally back-and-forth between a beginning and an end of the time interval.